It is well known to those skilled in the art that aromatic hydrocarbons and olefins are each a class of very important industrial chemicals which find a variety of uses in petrochemical industry. It is also well known to those skilled in the art that catalytically cracking gasoline-range hydrocarbons produces lower olefins such as, for example, propylene; and aromatic hydrocarbons such as, for example, benzene, toluene, and xylenes (hereinafter collectively referred to as BTX) in the presence of catalysts which contain a zeolite. The product of this catalytic cracking process contains a multitude of hydrocarbons including unconverted C.sub.5 +alkanes; lower alkanes such as methane, ethane, and propane; lower alkenes such as ethylene and propylene; C.sub.6 -C.sub.8 aromatic hydrocarbons; and C.sub.9 +aromatic compounds which contain 9 or more carbons per molecule. Recent efforts to convert gasoline to more valuable petrochemical products have therefore focused on improving the conversion of gasoline to olefins and aromatic hydrocarbons by catalytic cracking in the presence of zeolite catalysts. For example, a gallium-promoted zeolite ZSM-5 has been used in the so-called Cyclar Process to convert a hydrocarbon to BTX.
Olefins and aromatic hydrocarbons can be useful feedstocks for producing various organic compounds and polymers. However, the weight ratio of olefins to aromatic compounds produced by the conversion process is generally less than 50%. Additionally, a zeolite catalyst is generally deactivated in a rather short period, especially in a high sulfur and/or high polyaromatic environment, because of depositions of carbonaceous material, generally coke, on the surface of the catalyst. Moreover, the BTX purity in the product is generally not desirably high. Therefore, development of a catalyst and a process for converting hydrocarbons to the more valuable olefins and BTX and for reducing coke deposition would be a significant contribution to the art and to the economy.